1. Field of the Invention
The present invention relates to a small, light weight transmit-receive means for use in a phased-array active antenna system utilizing a multiplicity of individual transmit-receive cells, all mounted upon a common wafer of semiconductor material. Each transmitreceive cell comprises a plurality of redundant electronic devices that are selectively and permanently interconnectable by mitered mechanical switches.
2. Description of the Prior Art
Previous phased array active antenna systems for radar or electronic warfare applications utilized active FETs (field effect transistors), passive capacitors and phase shifting microstrip lines all manufactured on a multiplicity of individual monolithic chips. Each individual chip performed a separate functions such as; attenuation, digital and analog phase shift, power amplification, transmit/receive duplexing, and low-noise amplification. All of the individual chips were then mounted together on a cooled platen in a metallic assembly. This aggregation of individual chips constituted only one active element of a phased-array active antenna system. A complete phasedarray active antenna system required many or hundreds of such complex elements all mounted to a common matrix structure which provided radio frequency signals, logic command signals, and prime power to all array elements, as well as a means for thermal dissipation.
As well known in the prior art, for modern military aircraft, seven pounds (3,167.43 gms) of aircraft structure, jet engines and fuel are required for every pound (452.49 gms) of electronic equipment. Increased aircraft weight, however, translates directly to degraded aerodynamic performance. Only a lightweight, active aperture array system would be totally responsive to the electronic equipment requirements of modern military aircraft.
A standard phased-array active antenna system comprises; a means to produce a radio frequency signal, a transmit-receive means or duplexer which is operable to transmit or receive radio frequency signals, and a logic device, operable to shape the output beam from an antenna means.
The transmit-receive means or duplexer comprises; an attenuation means, a phase shifting means, a multistage amplification means, a low-noise amplification means, and appropriate transmitreceive switches which operate as a signal isolation means when the transmit-receive means is in either a transmit or receipt mode. Heat dissipation of heat away from the amplification means of the duplexer requires the use of heat sinks integrated with the duplexer to maintain operational temperatures for the circuits. Direct current, electrical energy is provided from a power generation means to the transmit-receive means devices.
Historically, a variety of systems of decreasing weight and size have been designed to achieve a lightweight antenna phased-array system. The patent to Stockton et al., U.S. Pat. No. 4,490,721 taught a monolithic microwave circuit including an integral array antenna. The Stockton invention included radiating elements, a feed network, phasing network, active and passive semiconductor devices, logic interface, and a microprocessor all incorporated on a gallium arsenside substrate. However, even with the incorporation of these devices on one substrate the Stockton invention perpetuated the individual element approach. Also, the lack of electronic device redundancy resulted in a low yield of operable chips. The reliance on this individual chip approach did not appreciably reduce the weight of the final antenna array with its multiplicity of individual elements. A multiple device or electronic device redundancy concept in the transmit-receive means would produce a high yield transmit-receive means. If a multiplicity of transmit-receive means are mounted onto a common semiconductor wafer a greater yield of operable devices would be the result.
The size of the antenna unit cell is constrained in that it cannot be any larger than 0.6 .lambda..sub.O is the free space wavelength given by this equation: EQU .lambda..sub.O min =(C/f.sub.H);
where
.lambda..sub.O =minimum free space wavelength PA1 c=3.times.10.sup.10 cm/sec. PA1 f.sub.H =highest operating frequency
The problem to be solved, then, is the manufacture of an active phased-array antenna system incorporating lightweight, redundant array elements operable for use in radar or broadband electronic warfare devices on advanced electronic systems.